CD4 and COVID-19: We observed many changes in productive proportional combinatorial V × J usage in TCRɑ CD4 repertoires (22 combinations up in COVID-19 group, with enrichment of combinations using TRAV9-2, and 22 combinations down) and CD8 repertoires (19 combinations up in COVID-19 group with enrichment of TRAV21, and 22 combinations down; Fig. 5B and D).